In recent years, increased attention has been directed toward improved energy efficiency in electronic equipment. International standards such as Energy Star provide energy consumption specifications that a product must meet if it is to be certified.
In order to reduce energy consumption, electronic equipment such as printers, typically have a normal operating mode during which prints can be made and a standby mode or a sleep mode during which prints cannot be made. In the standby or sleep mode, power is only supplied to certain key portions of the apparatus so that it is in a low power mode. For example, power can be provided to a microcontroller in sleep mode so that it is not necessary to reinitialize the firmware when it is time to re-enter normal operating mode. Thus a sleep mode provides energy savings while permitting rapid availability of the printing capability when needed. Even more power savings is possible by turning off the printer entirely, but turning the printer off results in some delay in the availability of printing capability when the printer is turned back on.
A printer typically enters the low power mode when there is no printing activity. For example, if image data is not received for printing for a predetermined period of time, the printer controller will switch the printer into a low power mode. The controller typically switches the printer back into normal operating mode when image data is received for printing, or when the user interacts physically with the printer by touching a key on the user interface for example. A special problem exists for printing systems having wireless communication capability. In this case, it is desirable to be able to send print jobs to such printing systems from remote locations for printing. If the printing system is in its operating mode, then the remotely sent print job will print out. However, for printing systems that disconnect power from the wireless communication device during a low power mode, the wireless receiver will fail to receive the remotely sent print job and therefore it will fail to print.
Consequently, a need exists for a printing system and a way to operate the printing system such that wireless communication to the printer is supported without drawing on AC line voltage in a low power mode so that energy efficiency requirements can be met without losing the ability to receive data for printing at any time.